1. Field of the Invention
The present invention relates to a mobile telecommunication system, and more particularly to a method and apparatus for processing uplink data by a terminal performing a discontinuous reception (DRX) mode operation in a mobile telecommunication system.
2. Description of the Related Art
The universal mobile telecommunication service (UMTS) system is a 3rd generation asynchronous mobile telecommunication system which is based on European mobile telecommunication systems, that is, GSM (Global System for Mobile Communications) and GPRS (General Packet Radio Services), and uses a CDMA (Code Division Multiple Access) scheme.
As a way to reduce terminal power consumption, the conventional 3rd generation mobile telecommunication system employs a discontinuous reception (DRX) mode in which a terminal transitions to an idle state when it has no data to transmit/receive, and discontinuously receives a paging message in the idle state. In other words, the terminal wakes up, that is, powers on its transceiver, at a predefined time, and monitors a paging channel. If the terminal receives a paging message over the paging channel, it transitions to a connection state. However, if the terminal receives no paging message, it powers off its transceiver, and maintains a sleep state until the next wakeup time.
The reason why the DRX mode is applied to a conventional idle-mode terminal is that the conventional mobile telecommunication system centers on a voice call, and thus the terminal stays in a connection state only for a relatively short time.
However, an evolved mobile telecommunication system, such as LTE (Long Term Evolution) that is currently under discussion, is expected to provide a terminal with a packet service, as well as the voice call. The terminal that is provided with the packet service may stay in a connection state for a relatively long time, and a problem to be solved in the evolved mobile telecommunication system is to minimize the power consumption of the terminal that may stay in a connection state for such a long time.
In the evolve mobile telecommunication system, therefore, a network may appropriately set up the DRX mode in consideration of the characteristics of services supported to a terminal that is in a connection state.
FIG. 1 illustrates the concept of a DRX operation.
Referring to FIG. 1, the DRX operation generally included the following elements:                Active State (or Active Period): A period during which a receiver of a terminal is turned on. In the active state, the terminal checks if there is downlink data, and receives data when the downlink data exists.        Sleep State (or Sleep Period): A period during which a receiver of a terminal is turned off. It is established for the minimization of terminal power consumption.        DRX Cycle Length 110, 120: A length between an active period and the next active period.        
Since the DRX operation as mentioned above is aimed at receiving data while minimizing terminal power consumption, the beginning and end of an active state is defined in connection with data reception. That is, the beginning point of an active state, the end point of an active state, etc. are determined by considering a data reception time, the amount of received data, and so forth.
In addition, uplink data may occur in a terminal that is in the above-mentioned DRX operation. A description will be given of how the DRX operation is affected by the uplink data occurring in a terminal that is in the DRX operation, with reference to FIG. 2.
Referring to FIG. 2, reference numeral “a” shows that a terminal performs a DRX operation consisting of active states 205, 210, 215 and 217 and sleep states.
Reference numeral “b” shows that when the terminal should perform a transmission operation according to the occurrence of uplink data in the terminal performing the DRX operation (as designated by reference numeral “220”), it must transition to an active state and perform the transmission operation 225 although it is in a sleep state of the DRX operation at a corresponding time.
Also, in response to the transmission operation 225, the transmission operation may be accompanied with an operation of transmitting an ACKnowledgement (ACK)/Non-ACKnowledgement (NACK) signal according to a Hybrid Automatic Repeat Request (HARQ).
When the HARQ operation is performed, the terminal maintains an active state so as to receive from a base station the ACK/NACK signal, which indicates whether or not the reception of the uplink data is erroneous.
Consequently, a period during which the terminal actually stays in an active state can be defined by the summation of active state periods of the DRX operation and an active state period for the transmission operation, as represented by reference numeral “c”.
For example, it is assumed that active state periods 205, 210, 215 and 217 for downlink data reception are established for any terminal, and uplink data occurs at a certain time “e” belonging to a sleep state period, according to which the terminal transitions to an active state (as designated by reference numeral “225”), and then maintains the active state until a time “f”.
Thus, the actual overall active state period of the terminal corresponds to the summation of the active state periods for data reception and the active state period for data transmission 230, 235, 240 and 245.
With regard to this, in order to ensure the efficiency of the DRX operation when the terminal transitions to the active state for data transmission, as described above, it is very important to define when the terminal ends the active state.
In the conventional mobile telecommunication system, such as the UMTS system, once a terminal transitions to an active state for uplink data transmission, the terminal maintains the active state until the receipt of a separate instruction from the network. That is, the terminal ends the active state and resumes the DRX operation under the control of the network.
In addition, the DRX operation in the conventional UMTS system targets an idle-mode terminal that is not accompanied by substantial data transmission/reception.
However, in the evolved mobile telecommunication system that is newly discussed based the UMTS system, a connection-mode terminal performs a DRX operation in correspondence to the packet service. This DRX operation is quite different from that of an idle-mode terminal accompanied by no data transmission/reception.